Initiator for tire inflator

ABSTRACT

The invention is a light, portable, miniaturized tire inflator adapted to fit in a limited space, such as in a tire well for a deflated, space-saving tire in a trunk of an automobile, and adapted to be carried or held in one hand. The tire inflator includes: a pyrotechnic material, an ignitor mechanism, a pressure vessel, and a nozzle. The pyrotechnic material generates an inflating gas upon burning to inflate a tire without a source of stored fluid. The ignitor mechanism is located adjacent to the pyrotechnic material to ignite and cause the pyrotechnic material to burn. The pressure vessel holds the pyrotechnic material. The pressure vessel has a tire end and a pyrotechnic end. The nozzle is mounted on the tire end of the pressure vessel. The nozzle is adapted to be connected directly to a valve of the tire. The nozzle includes a combined connection for the tire valve and initator for convening the chain reaction which will automatically result in the inflation of the tire on connection of the inflator to the tire.

This is a continuation of application Ser. No. 554,898, filed Mar. 3,1975, now abandoned.

BACKGROUND OF THE INVENTION

The invention relates to miniaturized apparatus for inflating apneumatic tire, such as a tire used on an automobile, truck, bicycle orother vehicle. The apparatus is small enough to fit in a limited space,such as in a tire well for a deflated, space-saving tire in a trunk ofan automobile or in a glove compartment of an automobile. The apparatusis light in weight, portable and can be carried or held in one hand bythe user. The apparatus is adapted to be attached directly to a valve ofa tire to inflate the tire. The inflating gas is derived solely fromburning a pyrotechnic material, preferably a slow burning, compactedpyrotechnic material. The apparatus does not use a stored fluid of anytype, neither a compressed nor a liquefied gas.

U.S. Pat. No. 1,008,646 to Kassner, issued in 1911, discloses anapparatus for inflating a tire which is transportable, but notminiaturized and which uses celluloid to generate a gas upon burning.The device of the Kassner patent is not attached directly to the tirevalve. Modern tire inflation apparatus have heretofore depended upon astored fluid, either compressed gas or liquefied gas, rather than a gasgenerated by burning a pyrotechnic material, as illustrated in U.S. Pat.Nos. 3,448,779 and 3,513,885 to Horwitt; U.S. Pat. No. 2,498,596 toWallace; and U.S. Pat. No. 2,218,931 to Carlson. The use of acomparatively faster-burning pyrotechnic material to inflate a vehiclesafety bag, without the use of a stored gas, is disclosed in U.S. Pat.Nos. 3,618,980 and 3,618,981 to Leising; and in U.S. Pat. applicationSer. No. 316,947, filed Dec. 20, 1972 which is a continuation of U.S.patent application Ser. No. 110,845, filed Jan. 29, 1971, both entitled"Gas Generator," both filed in the name of John J. Sack and Thomas E.Lohr, and both having a common assignee with the present invention.

Summary of the Invention

The invention is a light, portable, miniaturized tire inflator adaptedto fit in a limited space, such as in a tire well for a space-savingtire in a trunk of an automobile, and adapted to be carried or held inone hand. The tire inflator includes: a pyrotechnic material, an ignitormechanism, a pressure vessel, and a nozzle. The pyrotechnic materialgenerates an inflating gas upon ignition and burning to inflate a tirewithout a source of stored fluid. The ignitor mechanism is locatedadjacent to the pyrotechnic material to ignite and cause the pyrotechnicmaterial to burn. The pressure vessel holds the pyrotechnic material.The pressure vessel has a tire and a pyrotechnic end. The nozzle ismounted on the tire end of the pressure vessel. The nozzle is adapted tobe connected directly to a valve of the tire and includes the initiatorfor causing burning of the pyrotechnic material to supply gas forinflation.

DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 7 are prior art to this invention and the drawings anddesignation relating thereto are found in application Ser. No. 520,506filed Nov. 4, 1974 and assigned to the assignee of this application.

FIG. 1 is a cross-sectional view of a first embodiment of the tireinflator apparatus and a portion of a tire, including a tire valve, tobe inflated by the tire inflator apparatus.

FIG. 2 is an end view of FIG. 1 in the direction of arrow A in FIG. 1.

FIG. 3 is a cross-sectional view of a portion of FIG. 1 showing anoptional over-pressure relief valve, not shown in FIG. 1.

FIG. 4 is a cross-sectional view of a second embodiment of the tireinflator apparatus of this invention and a portion of a tire, includinga tire valve, to be inflated by the tire inflator apparatus.

FIG. 5 is an end view of FIG. 4 in the direction of arrow B in FIG. 4.

FIG. 6 is a partial cross-sectional view of FIG. 5 along the lines 6--6in FIG. 5.

FIG. 7 is an enlarged view of a portion of FIG. 4, showing a nozzle andthe ignitor mechanism.

FIGS. 8 and 9 show the nozzle and ignitor mechanism of the invention.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, the embodiment is a light portable, miniaturizedtire inflator, the first embodiment of which is referred to generally bythe numeral 2. The first embodiment 2 of the tire inflator includes: apyrotechnic material 4, an ignitor mechanism, referred to generally bythe numeral 6; a pressure vessel, referred to generally by the numeral8; and a nozzle, referred to generally by the numeral 10. Thepyrotechnic material 4 generates substantially non-toxic andnon-condensible inflating gas upon ignition and burning to inflate atire, without a source of stored fluid, either compressed gas orliquefied gas. The ignitor mechanism 6 is located adjacent to thepyrotechnic material 4 to ignite and cause the pyrotechnic material 4 toburn. The pressure vessel 8 holds the pyrotechnic material 4. Thepressure vessel 8 has an pyrotechnic end, at which the ignitor mechanism6 is located and a tire end at the opposite end of the pressure vessel 8from the pyrotechnic mechanism 6. The nozzle 10 is mounted on the tireend of the pressure vessel 8, at the opposite end of the pressure vessel8 from the ignitor mechanism 6. The nozzle 10 is adapted to be connecteddirectly to an inlet valve 7 of a tire 9 to inflate the tire 9. The term"directly" means that the nozzle 10 may be connected to a tire valve 7without any need for a hose or tube between the nozzle 10 and the tirevalve 7 without any need for a hose or tube between the nozzle 10 andthe tire valve 7. For example, the nozzle 10 may be screwed on the tirevalve 7.

The pressure vessel 8 includes a cannister 11 and a cannister cap 12.The cannister 11 has a cylindrical shape, a pyrotechnic end and a tireend. The tire end of the cannister 11 is open and has an outer edge 14.A portion of the cannister cap 12 is adapted to fit at, that is, eitherwithin or over the outer edge 14 of the tire end of the cannister 11. Ifthe cannister 11 is arranged to fit over the outer edge 14, the outeredge 14 of the tire end of the cannister 11 may optionally be slightlylarger in circumference as compared to the remainder of the cannister11. The cannister cap 12 includes a first plate 16 and an optionalcoolant bed 18. The coolant bed 18 is made up of chips of steel or sandor similar material adapted to cool the inflating gas as the gas passesthrough the coolant bed 18. The first plate 16 has slots or otherapertures through which the inflating gas passes to the nozzle 10. Thecannister cap 12 also includes an optional second plate 17 which alsohas slots or other apertures. The coolant bed 18 is disposed between thefirst plate 16 and the second plate 17. Both the first plate 16 and thesecond plate 17 are arranged with their approximately planar surfacessubstantially perpendicular to a longitudinal axis of the pressurevessel 8. The plates 16 and 17 may also be wire mesh screens.

The cannister 11 houses the pyrotechnic material 4. Preferably, thepyrotechnic material 4 occupies approximately half or slightly more thanhalf of the total volume of the cannister 11. Preferably, thepyrotechnic material 4 is made up of grains which are compacted, thatis, pressed together in the shape of a cylinder. The cannister 11 alsohas a plenum chamber 20 which includes the volume of the cannister 11between the cannister cap 12 and the pyrotechnic material 4. The plenumchamber 20 is located between the second plate 17 and the pyrotechnicmaterial 4. The plenum chamber 20 accommodates expansion of the gasgenerated by the pyrotechnic material 4. Preferably, the outer surfaceof the pyrotechnic material 4 between the pyrotechnic material 4 and thewalls of the cannister 11 and between the end of the pyrotechnicmaterial 4 adjacent to the plenum chamber 20 and the plenum 20 has acoating of a chemically inert inhibitor, such as a ceramic material.This coating keeps such outer surfaces of the pyrotechnic material 4from igniting or at least delays ignition on such outer surfaces of thepyrotechnic material 4 from igniting or at least delays ignition on suchouter surfaces of the pyrotechnic material 4. For example, the inhibitormay be Sauereisen #30 or Sauereisen #63 made by Sauereisen Company ofPittsburgh, Pa. The inhibitor is not used on the end of the pyrotechnicmaterial 4 adjacent to ignitor mechanism 6, but only on the end of thepyrotechnic material 4 further away from ignitor mechanism 6.

The ignitor mechanism 6 is adapted to ignite the pyrotechnic material 4and cause the pyrotechnic material 4 to burn. In the first embodiment 2of the tire inflator, the ignitor mechanism 6 is located at the oppositeend of the cannister 11 from the cannister cap 12 and the nozzle 10. Theignitor mechanism 6 includes: a striker 22, a biasing means (not shown)for the striker 22, a retaining member 24, a primer 26, and an ignitionmix 28. The striker 22 has a pivot point 30 at one end, an actuatedposition, and a non-actuated position. The biasing means may be a coilspring located at the pivot point 30 of the striker 22, biasing thestriker 22 in a pivoting direction to pivot clockwise on the pivot point30 from the non-actuated position of the striker 22 to the actuatedposition of the striker 22.

In FIG. 1, the striker 22 is shown in its non-actuated position. Theretaining member 24 is adapted to retain the striker 22 in itsnon-actuated position. The retaining member 24 has a pivot support 32 atone end to support the pivot point 30 of the striker 22 and the biasingmeans 24 for the striker 22, and a catch 34 at the opposite end of theretaining member 24 to retain the striker 22 in its non-actuatedposition as shown in FIG. 1. The catch 34 is adapted to be pressed in adirection toward the pressure vessel 8. The catch end of the retainingmember 24 adjacent to the catch 34 is resilient enough to bend and toallow the catch 34 to release the striker 22. The striker 22 has afiring head 36, which may have a conical shape. The primer 26 is apercussion actuated primer adapted to be actuated by the striker 22 toprovide a thermal signal which initiates combustion of the ignition mix28. The primer 26 is sensitive to shock resulting from the impact of thefiring head 36.

When the catch end of the retaining member 34 is pressed down, i.e.toward the cannister 11, the striker 22 is released. The biasing means,such as a coil spring, spring loads the striker 22 and causes thestriker 22 to pivot approximately 180 degrees upon its pivot point 30 tothe actuated position of the striker 22. In its actuated position, thefiring head 36 of the striker 22 hits the primer 26. The primer 26initiates combustion of the ignition mix 28 disposed in an ignition cup38, which generates hot gas and hot particles, which ignite thepyrotechnic material 4. Combustion of the pyrotechnic material 4produces the inflating gas for the tire 9. The pyrotechnic material 4 isthe sole source of inflating gas for the tire. There is no stored fluid,neither compressed gas nor liquified gas.

The pyrotechnic material 4 has an ignition end adjacent to the ignitionmechanism 6 and a nozzle end adjacent to the cannister cap 12. Theinflating gas is initially generated at the ignition end of thepyrotechnic material 4. A gas permeable structure, such as a corrugated,expanded or perforated metal structure, preferably a metal screen 40 isdisposed around the outer circumference of the pyrotechnic material 4between the pyrotechnic material 4 and the cannister 11 for the purposeof allowing gas generated at the ignition end of the pyrotechnicmaterial 4 to pass between the outer circumference of the pyrotechnicmaterial 4 and the cannister 11 as the gas moves toward the plenumchamber 20.

The nozzle 10 has a tire end and a pyrotechnic end. The pyrotechnic endof the nozzle 10 is connected to a mouth 41 of the cannister cap 12. Thetire end of the nozzle 10 has means, such as screw threads, to attachthe nozzle 10 directly to means on the tire valve 7, such as screwthreads 43 on the outer circumference of tire valve 7. The tire end ofthe nozzle 10 has a well 42. The tire end of the nozzle 10 is adapted tofit over and around the outer circumference of tire valve 7. The well 42is dimensioned so that the tire valve 7 fits into the well 42. The screwthreads or other attachment means are located in the well 42 on theinside walls of the nozzle 10. The nozzle 10 also includes an optionalstem depressor 44 for depressing the valve stem 45 of the tire valve 7to allow inflating gas to pass through the tire valve 7 into the tire 9.The stem depressor 44 is a stationary pin which extends through a nozzlebore 46 in the pyrotechnic end of the nozzle 10. The nozzle bore 46extends from the pyrotechnic end of the nozzle 10 to the well 42 of thenozzle 10. The nozzle bore 46 conducts inflating gas from the pressurevessel 8 around the stem depressor 44 to the well 42. The stem depressor44 is fixedly attached to the slotted plate 14.

An insulator 48 is provided around the outer circumference of thepressure vessel 8. The insulator 48 is cylindrical in shape and extendsfrom the cannister cap 12 along approximately 80% of the length of thecannister 11. The insulator 48 may include one or preferably two layersof an insulating material, such as corrugated paper, plastic, or metal.

A safety cap 50 is disposed over the ignitor mechanism 6 and around theignitor end of the cannister 11. Preferably, safety cap 50 is attachedto or in abutting contact with the insulator 48. The outside end of thesafety cap 50 opposite from the insulator 48 has a membrane 52 around amajor part of the circumference of the safety cap 50. The membrane 52 isadapted to be ruptured by the user, such as by use of his thumb. Thesafety cap 50 also has an indented portion 53 at the opposite side ofthe safety cap 50 from the membrane. The indented portion 53 functionsas a hinge after the membrane 52 is ruptured, enabling safety cap 50covering the ignitor mechanism 6 to be bent back upon the indentedportion 53, providing access to the ignitor mechanism 6.

In operation, the user removes the safety cap 50, attaches the nozzle 10to the tire valve 7 to depress the valve stem 45 and depresses the catch34. This releases the striker 22 which hits the primer 26. This ignitesthe ignitor mix 28 which causes the pyrotechnic material 4 to burn. Theinflating gas generated upon combustion passes through the metal screen40, the plenum chamber 20, the coolant bed 18, the nozzle bore 46, thewell 42, and the tire valve 7 and into the tire 9.

Referring to FIGS. 4-7, the second embodiment of the tire inflator ofthe prior art is referred to generally by the numeral 102. The secondembodiment 102 includes: a pyrotechnic material 104, an ignitormechanism, referred to generally by the numeral 106; a pressure vessel,referred to generally by the numeral 108; and a nozzle, referred togenerally by the numeral 110. The pyrotechnic material 104 is similar tothat used for the first embodiment 2, illustrated in FIGS. 1-3. Theignitor mechanism 106 is located adjacent to the pyrotechnic material104 to ignite and cause the pyrotechnic material 104 to burn, althoughthe ignitor mechanism of 106 is not as close to the pyrotechnic material104 as the ignitor mechanism 6 in the first embodiment 2. The pressurevessel 108 holds the pyrotechnic material 104. The pressure vessel 108has a pyrotechnic end and a tire end. In contrast to the firstembodiment 2, the ignitor mechanism 106 of the second embodiment 102 islocated at the tire end of the pressure vessel 108, at the opposite endof the pressure vessel 108 from the pyrotechnic end. The nozzle 110 isalso mounted on the tire end of the pressure vessel 108. The nozzle 110is adapted to be connected directly to an inlet valve 7 of the tire 9 toinflate the tire 9, in the same manner as the nozzle 10 of the firstembodiment 2.

The pressure vessel 108 includes a cannister 111 and a cannister cap112. The cannister 111 has a cylindrical shape, a pyrotechnic end and atire end. The tire end of the cannister 111 is open and has an outeredge 114. A portion of the cannister cap 112 is adapted to fit at, thatis, either within the outer edge 114 or over the outer edge 114 of thetire end of the cannister 111. The cannister cap 112 includes a firstplate 116 and an optional coolant bed 118. The coolant bed 118 is madeup of chips of steel or sand or similar material adapted to cool theinflating gas as the gas passes through the coolant bed 118. The firstplate 116 has slots or other apertures through which the inflating gaspasses to the nozzle 110. The cannister cap 112 also includes anoptional second plate 117 which also has slots or other apertures. Thecoolant bed 118 is disposed between the first plate 116 and the secondplate 117. Both the first plate 116 and the second plate 117 arearranged with their approximately planar surfaces substantiallyperpendicular to a longitudinal axis of pressure vessel 108. The plates116, 117 may also be wire mesh screen.

The cannister 111 houses the pyrotechnic material 104. Preferably, thepyrotechnic material 104 occupies approximately half or slightly morethan half of the total volume of the cannister 111. Preferably, thepyrotechnic material 104 is made up of grains which are compacted, thatis, pressed together in the shape of a cylinder. The cannister 111 alsohas a plenum chamber 120 which includes the volume of the cannister 111between the cannister cap 112 and the pyrotechnic material 104. Theplenum chamber 120 is located between the second plate 117 and thepyrotechnic material 104. The plenum chamber 120 accommodates expansionof the gas generated by the pyrotechnic material 104. The pyrotechnicmaterial 104 of the second embodiment 102 may have the same compositionas the pyrotechnic material 4 of the first embodiment 2. But thepyrotechnic material 104 differs as to which outer surfaces have acoating of inhibitor. Preferably, the outer surface of the pyrotechnicmaterial 104 between the pyrotechnic material 104 and the walls of thecannister 111 and the end of pyrotechnic material 104 further away fromthe plenum chamber 120, that is, the end of the pyrotechnic material 104further away from the ignitor mechanism 106, have a coating of achemically inert inhibitor, such as a ceramic material. This coatingkeeps such outer surfaces of the pyrotechnic material 104 from ignitingor at least delays ignition of such other surface of the pyrotechnicmaterial 104. For example, the inhibitor may be Sauereisen #30 orSauereisen #63 made by Sauereisen Company of Pittsburgh, Pa. In both thefirst embodiment 2 and the second embodiment 102, the inhibitor is notused on the end of the pyrotechnic material 104 adjacent adjacent toignitor mechanism 106 but only on the end of the pyrotechnic material104 further away from the ignitor mechanism 106.

Referring to FIGS. 4 and 7, the nozzle 110 has a nozzle body 169 whichhas a tire end and a pyrotechnic end. The pyrotechnic end of the nozzlebody 169 extends through a mouth 141 of the cannister cap 112 and amouth 138 of the first plate 116. The tire end of the nozzle body 169has means, such as screw threads, to attach the nozzle 110 directly tomeans on the tire valve 7, such as screw threads 43 on the outercircumference of the tire valve 7. The tire end of the nozzle body 169has a well 142. The tire end of the nozzle body 169 is adapted to fitover and around the outer circumference of tire valve 7. The well 142 isdimensioned so that the tire valve 7 fits into the well 142. The screwthread or other attaching means of the nozzle body 169 are located onthe inside walls of the well 142. The nozzle 110 also includes anoptional stem depressor 144 for depressing the valve stem 45 of the tirevalve 7 to allow inflating gas to pass through the tire valve 7 into thetire 9. The stem depressor 144 is a stationary pin which extends througha longitudinal nozzle bore 146 in the pyrotechnic end of the nozzle body169.

The ignitor mechanism 106 is adapted to ignite the pyrotechnic material104 and cause the pyrotechnic material 104 to burn. In the secondembodiment 102 of the tire inflator, the ignitor mechanism 106 islocated at the tire end of the cannister 111. The ignitor mechanism 106extends through the mouth 138 of the first plate and through an aperture136 in the second plate 117. The ignitor mechanism 106 is locatedimmediately adjacent to and at a pyrotechnic end of the nozzle body 169.Referring to FIG. 7, the ignitor mechanism 106 includes: an ignitor body170, an actuator tube 172 having a flange 174, a washer 176, a spider178, a coil spring 182, a plunger, a shear pin 186, a firing pin 188, aplunger cavity 190, a star washer 192, a primer 194, a flash hole 196, acolumn of an intermediate ignition material 198, a main ignition charge200 and a nozzle plate 202.

The main ignition charge 200 is a hotter and faster burning pyrotechnicmaterial than the pyrotechnic material 104 diposed in the pressurevessel 108. The main ignition charge 200, for example, may be Arcite497-C, manufactured by Atlantic Research Corporation and disclosed inU.S. Pat. No. 2,966,403 to L. L. Weil, entitled "Solid PropellantCompositions and Processes for Making Same". The intermediate ignitionmaterial 198 may be a column of aluminum/iron oxide (Fe₂ O₃). Theintermediate ignition material 198 and the main ignitor charge 200,together, act as an ignition means, adapted to be ignited by the primerto cause combustion of the pyrotechnic material 104.

The ignitor body 170 extends through the cannister cap 112 and into aportion of the cannister 111. The actuator tube 172 functions as anactuator member and has a tire end and pyrotechnic end. The actuatortube 172 is disposed within the nozzle bore 146 and a portion of alongitudinal ignitor bore 171 in the ignitor body 170. The actuator tube172 has a tire end and a pyrotechnic end. The flange 174 is located atthe tire end. The stem depressor 144 is axially disposed within the tireend of the actuator tube 172 and the stem depressor 144 extends out ofthe actuator tube 172 and into the well 142. The actuator tube 172 ismovable within the nozzle bore 146 and the ignitor bore 171 by the tirevalve 7. When the second embodiment 102 of the tire inflator is attachedto the tire valve 7, the tire valve 7 abuts the flange 174 of theactuator tube 172 and moves the actuator tube 172. The shear pin 186 isdisposed in the ignitor body 170 substantially radially to the ignitorbore 171 of the ignitor body 170 and extends into part of the ignitorbore 171. The shear pin 186 is a breakable member adapted to be brokenby the actuator tube 172 when the actuator tube 172 is moved by the tirevalve 7. The coil spring 182 is a driving member disposed inside aportion of the actuated tube 172 and adapted to be released by the shearpin 186 when the shear pin 186 breaks. Before the second embodiment 102of the tire inflator is placed on the tire valve 7 for use, the coilspring 182 is in a compressed condition. The coil spring 182 is held inits compressed condition by the shear pin 186. When the shear pin 186 isbroken, the coil spring 182 is released from its compressed positionwhich allows the coil spring 182 to expand. The plunger has a plungertail 184 at its tire end and a plunger head 185 at its pyrotechnic end.The plunger tail 184 extends partially into a pyrotechnic end of thecoil spring 182. The plunger head 185 has a firing pin 188 at thepyrotechnic end of the plunger head 185. The plunger head 185 and firingpin 188 are driven by the coil spring 182 when the coil spring 182expands. The primer 194 is adapted to be actuated by the firing pin 188by impact of the firing pin 188 upon the primer 194 when the primer 194is driven by the coil spring 182. The intermediate ignition material 198is adapted to be ignited by the primer 194. The intermediate ignitionmaterial 198 then ignites the main ignition charge 200. The mainignition charge 200 is then ignited and causes combustion of thepyrotechnic material 104.

The ignitor body 170 is adjacent to, aligned and continuous with thenozzle body 169 and preferably integral with the nozzle body 169. Theignitor body 170 and nozzle body 169 have at least one gas passage and,preferably, two gas passages 134 extending radially into the nozzle bore146. A support means for the actuator tube 172 includes the washer 176and the spider 178. The stationary washer 176 is disposed around anouter cicumference of the actuator tube 172 at the tire end of theactuator tube 172 to support the actuator tube 172 and act as a gas sealfor the inflating gas to prevent the inflation gas from escaping betweenthe interior sides of the well 142 and the tire valve 7. The stationaryspider 178 is also disposed around the actuator tube 172 on thepyrotechnic side of the washer 176 to support the actuator tube 172 andthe stem depressor 144. The spider 178 has fingers extending radiallyfrom the spider 178 into longitudinal slots in the actuator tube 172.The longitudinal slots in the actuator tube 172 allows the actuator tube172 to slide or move through the stationary spider 178. The plungercavity is in the longitudinal ignitor bore 171 of the ignitor body 169.The plunger head 185 and firing pin 188 are adapted to move through theplunger cavity 190. A primer cavity 180 in the longitudinal bore 171holds the primer 194. The star watcher 192 holds the primer 194 inposition in the primer cavity 180. The flash hole 196 conducts a thermalsignal from the primer 194 to the column of intermediate ignitionmaterial 198. A cavity for holding the intermediate ignition material198 is smaller than a cavity to hold a main ignition charge.

In operation, when the nozzle 110 is screwed on the tire valve 7, orotherwise attached to the tire valve 7, the tire valve 7 extends intothe interior of the well 142 of the tire end of the nozzle 110. The stemdepressor 144 of the nozzle 110 presses upon the valve stem 45 of thetire valve 7, depressing the valve stem 45 and opening the tire valve 7to allow entry of inflating gas into the tire 9. The outer end 47 of thetire valve 7 presses against the flange 174, moving the actuator tube172 within the longitudinal bore 171 of the ignitor body 170 toward thepyrotechnic end of the ignitor body 170. The movable actuator tube 172is allowed to slide to the right as shown in FIG. 7 in the nozzle bore176 by longitudinal slots in the actuator tube 172 which allow theactuator tube 172 to pass through the stationary spider 178. Movement ofthe actuator tube 172 breaks the shear pin 186. Breakage of the shearpin 186 allows the compressed coil spring 180 to expand and move towardthe right as shown in FIG. 7. The coil spring 180 expands against theplunger 184 moving the plunger 184 and firing pin 188 to the rightthrough the plunger cavity 190, and causing the firing pin 188 to impactagainst the primer 194.

THe primer 194 is held in position by the star washer 192 in order toallow the primer 194 to function as a gas seal to prevent passage of thegas through the cavity 180 occupied by the primer 194. The thermalsignal from the primer 194 acts through a flash hole 196 and ignites acolumn of Thermite (aluminum-iron oxide Fe₂ O₃), or other intermediateignition material 198 which in turn ignites the main ignition charge200. The hot gases from the main ignition charge 200 passed through ahole 203 in the nozzle plate 202 to ignite the pyrotechnic material 104.The inflating gas passes through the coolant bed 118, the gas passages134, the longitudinal slots of the actuator tube 172, into the actuatortube 172, through the well 142, the tire valve 7 and into the tire 9.

The second embodiment 102 of the tire inflator has an insulator 148provided around the outer circumference of the pressure vessel 108, withinsulator end portions 150, around both ends of the pressure vessel 108.The insulator 148 is cylindrical in shape (as shown in FIG. 5) andextends slightly beyond the length of the pressure vessel 108 at eachend. The insulator 148 and 150 may include one or preferably two layersof insulating material, such as corregated paper or plastic. In contrastto the first embodiment 2, the second embodiment 102 does not have anignitor cap 50. Instead of ignitor cap 50 which is used on the firstembodiment 2, the second embodiment 102 merely has an end portion 150 ofinsulator 148.

For both the first embodiment 2 and the second embodiment 102, theplenum chambers 20 and 120 allow growth of the pyrotechnic material 4and 104 during combustion. The pyrotechnic material 4 and 104 uponcombustion generates two products: an inflating gas and a residue whichremains behind in the cannister. The residue from the pyrotechnicmaterial 4 and 104 expands in volume to occupy a greater volume than thevolume previously occupied by the pyrotechnic material 4 and 104 beforecombustion. The plenum chambers 20 and 120 provide the necessary spacefor expansion of this residue. Allowing space for such growth in theresidue by means of the plenum chambers 20 and 120 facilitates lowerpressure and, hence, slower rates of combustion of the pyrotechnicmaterial 4 and 104. If it were desired to increase the combustion rateof the pyrotechnic material 4, this could be accomplished by providing asmaller plenum chamber or providing no plenum chamber at all. Theabsence of such expansion space would increase the pressure and, hence,cause faster burning.

Referring to FIGS. 2, 5 and 6, both the first embodiment 2 and thesecond embodiment 102 of the tire inflator have an over pressure reliefmeans 54 provided in the cannister caps 12 and 112. The over-pressurerelief means 54 is a safety device for release of excess pressure in thepressure vessels 8 and 108. The relief means 54 operates in conjunctionwith an aperture 56 in the cannister caps 12 and 112. The over-pressurerelief means 54 may be a rupture disc 58, as illustrated in FIG. 1 or arelief valve 60, as illustrated in FIG. 3. Referring to FIGS. 1 and 6,the rupture disc 58 is adapted to rupture if the pressure in thepressure vessels 8 and 108 exceeds a predetermined pressure level. Theruptured disc 58 is adapted to rupture at a pressure level lower thanthe pressure level at which the pressure vessels 8 and 108 wouldrupture. The rupture disc 58 is disposed inside the cannister caps 11and 111 and covers the aperture 56.

Referring to FIG. 3, the optional over-pressure relief valve 60 isdisposed on the cannister caps 12 and 112 in place of the rupture disc58 shown in FIG. 1. The relief valve 60 includes a disc 62 adapted tofit on the outer surface of the cannister caps 12 and 112, over theaperture 56. The relief valve 60 also has a plurality of prongs 64,preferably two prongs, extending from the disc 62 into the interior ofthe cannister caps 12 and 112. The prongs 64 may be press fit into theaperture 56 and resiliently engage the inner surface of cannister caps12 and 112. The over pressure relief valve 60 is adapted to rupture orbe blown out of the aperture 56 at a pressure which is lower than thelevel of pressure which the pressure vessels 8 and 108 can withstand.For example, a pressure in the range of about 300 psi (about 21.09 kg.per sq. cm) is normally developed in the pressure vessels 8 and 108after ignition of the pyrotechnic material 4 and 104. The rupture disc58 or the relief valve 60 may be designed to rupture at about 500 psi(about 35.15 kg. per sq. cm.) whereas the pressure vessels 8 and 108 maybe designed to withstand pressures of about 1000 psi (about 70.3 kg. persq. cm.) or higher.

The nozzles 10 and 110 also have a removable nozzle cap 68 over the tireend of the nozzles 10 and 110. The nozzle cap 68 covers the wells 42 and142. The nozzle cap 68 is adapted to be removed when the tire inflatoris about to be used. For example, the nozzle cap 68 may be a peelableadhesive.

Preferably, the tire inflator has a total length of less than about 10inches (about 25.4 centimeters).

The pyrotechnic material 4 and 104 may have a composition such as thatdisclosed in U.S. patent application Ser. No. 500,810 filed Aug. 26,1974, entitled "Low Temperature Gas Generated Propellant", which is acontinuation-in-part application of parent application Ser. No. 395,481,filed Sept. 10, 1973, entitled "Pyrotechnic Composition with CombinedBinder-Coolant", both filed in the name of E. F. Garner and having acommon assignee with the present invention. In general, the pyrotechniccomposition comprises a fuel; an inorganic oxidizer; and a coolant orcombined binder and coolant (which also is referred to as just a coolantin the following description). The coolant is selected from the groupconsisting of magnesium carbonate, magnesium hydroxide, and a mixture ofmagnesium carbonate and magnesium hydroxide. It has been found that onemay use as much of the binder-coolant as is necessary in the pyrotechnicmaterial 4 and 104 to obtain the desired binder properties for thecomposition without raising the flame temperature of the gas, generatedupon combustion, to an unacceptable level. The fuel may be selected fromthe group consisting of a carbonaceous material (such as carbon, carbonblack or lamp black), aluminum and magnesium. The inorganic oxidizer maybe selected from the group consisting of an alkali metal chlorate (suchas potassium chlorate or sodium chlorate), an alkali metal perchlorate(such as potassium perchlorate or sodium perchlorate), an alkali metalnitrate (such as potassium nitrate or sodium nitrate). The coolant orcombined binder and coolant may be selected from the group consistingof: magnesium carbonate, magnesium hydroxide, and a mixture of magnesiumcarbonate and magnesium hydroxide. A typical formulation of thispyrotechnic composition comprises: carbon which acts as a fuel;potassium chlorate (KClO₃) or potassium perchlorate (KClO₄) which actsas an oxidizer; and magnesium carbonate (MgCO.sub. 3) which acts as acoolant and binder.

In the case of the composition of carbonaceous fuel, inorganic oxidizerand magnesium carbonate coolant, a low temperature gas (about 800° F. orabout 426.5° C. in one embodiment) is generated relatively slowly (in,for example, about 1 to 3 seconds). Optionally, the gas is cooled bycontact with the metal chip coolant bed 18 or 118, to a temperature offrom about 200° F. to about 600° F. (from about 93° C. to about 315.5°C.), for inflating the tire 9.

The pyrotechnic material 4 and 104 comprises by weight: from less than1% to about 10% of one of the foregoing fuels, such as carbon; fromabout 30% to about 70% of one of the foregoing inorganic oxidizers, suchas potassium chlorate; and from about 10% to about 60% of one of theforegoing coolants or combined binders and coolants, such as magnesiumcarbonate or a mixture of magnesium carbonate and magnesium hydroxide.

Preferably, in one embodiment, the pyrotechnic composition comprises byweight: about 1% to about 5% of one of the foregoing fuels, such ascarbon; about 40% to about 60% of one of the foregoing inorganicoxidizers, such as potassium chlorate; and about 35% to about 55% of oneof the foregoing combined binders and coolants, such as magnesiumcarbonate or a mixture of magnesium hydroxide and magnesium carbonate.When such compositions are exposed to the atmosphere, the magnesiumhydroxide reacts with carbon dioxide (CO₂) in the air to form magnesiumcarbonate (MgCO₃). Magnesium carbonate is a highly oxygenated,cement-like material. Since magnesium hydroxide and magnesium carbonateare both coolants, not fuels, one can use as much as necessary. As aresult, one has enough binder for the composition without raising theflame temperature of the gas to unacceptable levels. The free oxygenformed from the inorganic oxidizer, such as potassium perchlorate, isconsumed by the fuel, such as carbon, forming carbon dioxide andevolving heat which is cooled by the decomposed magnesium carbonate.

In the pyrotechnic composition described in the fore-going paragraph, itis preferable, in most instances, to start with a mixture of magnesiumhydroxide and magnesium carbonate, rather than magnesium hydroxidewithout magnesium carbonate. One should use enough magnesium hydroxidein the mixture to obtain the desired binding effect caused by thecarbonation of the magnesium hydroxide. It has been found that thehigher the proportion of magnesium hydroxide to magnesium carbonate thatis used in the composition, the longer the reaction time will take.

In instances where mixtures of magnesium hydroxide and magnesiumcarbonate is used as the combined binder and coolant, the compositionmay comprise: from about 10% to about 30% magnesium hydroxide ascompared to the entire composition and from about 20% to about 40%magnesium carbonate as compared to the entire composition. In manycompositions it has been found advantageous for the mixture of magnesiumhydroxide and magnesium carbonate to comprise about 1/2 magnesiumhydroxide and about 1/2 magnesium carbonate.

A preferred embodiment has carbon as the fuel; potassium chlorate orperchlorate as the oxidizer; and magnesium carbonate as the coolantwithout using magnesium hydroxide. The relatively slow burningcomposition produces a relatively low temperature gas (which mayoptionally be further cooled as already discussed). It has beensurprisingly found that the carbon fuel burns in the presence of theoxidizer at a very high temperture, but relatively slowly, with themagnesium carbonate decomposing to absorb the heat and produce therelatively low temperature gas product made up of, substantially, carbondioxide (CO₂) and oxygen, with trace amounts of carbon dioxide (CO). Onepyrotechnic composition which has been found to be particular desirableincludes, by weight: about 3% carbon, about 45% potassium chlorate, andabout 52% magnesium carbonate.

The foregoing compositions of pyrotechnic material 4 and 104 generate,upon combustion, a substantially non-toxic, non-condensable gas adaptedto inflate a tire. The foregoing compositions are superior to celluloidbecause celluloid, upon combustion, would generate large amounts oftoxic gas (carbon monoxide and nitric oxides) and steam (which wouldcondense to water in a tire). The pyrotechnic materials 4 and 104 have asomewhat slower burning composition than a composition used to inflate avehicle safety bag.

For both embodiments, the stem depressor 44 and 144 is optional becausethe pyrotechnic material 4 and 104 may be arranged to generate enoughpressure to open the tire valve 7 without the use of a stem depressor 44or 144.

In FIG. 8, as compared to the prior art of FIGS. 1-7, the embodiment ofthis invention with the combined nozzle and firing pin structure isshown in unassembled condition. The firing pin assembly 500 includes afiring pin 501 and a firing pin extension 502 with elongated arms 503and prongs 504 and 505 extending in a plane perpendicular thereto. Aspring 600 will serve to bias or load the firing pin assembly 500. Thenozzle 700 which attached to the tire valve includes a body withshoulder 701 for receiving the spring 600 between the firing pin 501 andshoulder 702 for catching the prongs 504 and 505 when the firing pinassembly 500 is in loaded position with the spring 600 compressed.

The combined nozzle and firing pin structure is shown loaded in FIG. 9with a cap 703 over the nozzle end 710 which will attach to the tirevalve and be located within the longitudinal bore, as discussed indetail with relation to FIGS. 4 to 7.

The improvement of this embodiment of FIGS. 8 and 9 eliminates the needof a sheer pin to activate the firing pin (which is driven by the forceof the spring) toward and into contact with the primer 800 whichactivates the gas producer when the connection of the nozzle at the tireend to the tire valve removes the prongs 504 and 503 from the shoulder702.

The cap 703 is especially advantageous since it includes an extension720 which extends into the well of the nozzle and fits between the arms503 of the firing pin extension to prevent the prongs from beingdisengaged from the shoulder 702 accidentally.

We claim:
 1. A light, portable, miniaturized tire inflator for inflatinga tire having an inlet valve, and adapted to be carried in one hand,comprising:a pyrotechnic material as sole source of inflating gas togenerate the inflating gas upon combustion to inflate the tire, withouta source of stored fluid; an ignitor mechanism located adjacent to saidpyrotechnic material to ignite and cause said pyrotechnic material toburn; a pressure vessel to hold said pyrotechnic material, saidpresssure vessel having a tire end and a pyrotechnic end; and a nozzlemounted on said tire end of said pressure vessel, said nozzle beingadapted to be connected directly to the valve of the tire; said ignitormechanism including a firing pin assembly comprising a firing pin andlegs extending therefrom movable with a longitudinal bore adjacent saidnozzle by said tire valve; a spring for biasing said firing pinassembly; prongs on the end opposite of said legs to said firing pin;shoulder means on said bore adjacent said nozzle for engaging saidprongs and retaining said firing pin assembly against said springunloaded condition; a prime spaced from said firing pin in loadedcondition and adpated to be actuated by said firing pin by impact ofsaid firing pin upon said primer on disengagement by said tire valve ofsaid prongs from said shoulder means; an ignition means adapted to beignited by said primer and cause combustion of said pyrotechnicmaterial; and an insulator disposed around substantially the entireexterior surface of said pressure vessel.
 2. The tire inflator apparatusaccording to claim 1 and further comprising a cover for said nozzlewhich includes an extension from the cover to engage the legs of thefiring pin assembly and maintain the prongs on the shoulder.